Computer input devices such as the keyboard, touchscreen and mouse are well known. However these comprise moving parts and are thus subject to wear. Wired input devices which are at least in part worn or held by the user, are known from U.S. Pat. Nos. 4,682,159 and 4,988,981.
In some cases wires are found to be inconvenient or otherwise undesirable, and there are thus known wireless cursor manipulation devices which are worn or held by a user and examples are known from U.S. Pat. Nos. 5,444,462, 5,453,759, 5,754,126, 5,736,976, 5,638,092, 5,790,100, 5,489,922 and 5,729,475.
Systems in which no device is either worn or held by the user and which use electromagnetic radiation to monitor the location of a body part are known from U.S. Pat. Nos. 5,717,413 and 5,686,942. In the latter case it is also disclosed to use ultrasonic waves.